Analysis On The Stress Of Prestressed Concrete Cylinder Pipe During Wire Winded

In recent years, with the rapid development of Prestressed Concrete Cylinder Pipe(PCCP) in China, PCCP has been widely used in water conservancy, electric power, municipal water supply and drainage and other related engineering fields,especially the key project of China in recent years- South-to-North Water Diversion Project. Since the middle route of south-to-north water diversion project in Henan Province started, technical personnel found the surface of PCCP tube core concrete cracked during the period of production, transportation, parking and installation of PCCP, which is extremely common. Combined with the emerging issues in south-to-north water diversion project and other projects, this paper focuses on the wire wrapped during production process of PCCP, the stress change rules of PCCP tube core concrete during the wire wrapped, and the stress concentration phenomenon in spiral weld of steel cylinder by finite element analysis method, finally it studies the effect of the above issues on PCCP tube core concrete’s cracks.This paper summarizes the development of PCCP, research status and research methods related PCCP pipeline structure in the domestic and abroad. According to the production process and the characteristics of PCCP-E, combined with related engineering production data, a PCCP’s wire wrapping process finite element analysis model is established by finite element software ANSYS. The model is prestressed by the equivalent load method, and calculated after the entire wire wrapping process is divided into seven different conditions(wrapping position reaches 1m, 2m, 3m, 4m,5m, 6m and pipeline is horizontal when wire wrapping is completed), considering the coordination between the different materials and steel tube spiral weld’s lap level.Based on the calculation results, the following conclusions are obtained:(1)The steel tube spiral weld can cause stress concentration in tube core concrete during wire wrapping process. When overlapping step is 1.5mm, the stress concentration factor is1.39; and when overlapping step is 2.0mm, the stress concentration factor is1.50;(2)There are radial tensile stress, hoop tensile stress and axial tensile stress in inner and outer concrete during wire wrapping process, wherein the effect of axial tensile stress on tube core concrete’s cracks is the greatest, and inner concrete is more cracking than outer concrete;(3) For the inner concrete, the maximum axial tensile stress arises when wire wrapping process is completed half and more. The maximum axial tensile stress always arises behind wire wrapping position 0.4m during wire wrapping process.(4) For the inner and outer concrete, the development tendency of hoop stress are basically consistent, which are mainly compressive stress. Therefore,longitudinal cracks don’t arise in tube core concrete during wire wrapping process.(5)After wire wrapping is completed, all tensile stress of inner and outer concrete are extremely small when pipe is placed vertically and horizontally, not causing longitudinal cracks and circumferential cracks. Thus circumferential cracks in the inner concrete arise during wire wrapping process, don’t arise after wire wrapping is completed. Therefore, in order to reduce the generation of cracks caused by prestressing in production process, we should pay more attention to control of axial tensile stress during wire wrapping process.